See attachment for math work and answer.
Here to solve the equation we need to plug in the value y as given. -5x+2(7x)=9. -5x+14x=9. 9x=9. X=1.
I think its B , because if you connect the TWO dots forming a triangle its 3 up and 4 to the right making 3/4 as the slope and the Y intercept is 1 so y=3/4x +1
20% of 1000 = 200
40% of 200 = 80
Therefore there are 80 red sneakers
Hope this helps :)